Thyroid hormone is essential for regulation of cell metabolism. Hyperthyroidism is an elevation of thyroid hormone levels. It is a common condition affecting up to 1.3% of the population. Muscle weakness involving the shoulders and hips is a well-recognised complication and affects 60-80% of patients with untreated hyperthyroidism. Despite hyperthyroidism being a common cause of muscle weakness, the mechanism for how high thyroid hormone levels results in weakness remains unclear; however, several theories based on animal models have been proposed.
Muscle excitability is a novel electrical technique used to study muscle cells. It is a quick, repeatable test that provides a means to look at the electrical state of muscle cells in vivo. This is a potentially powerful technique that is furthering the understanding of muscle disease and may eventually aid in its diagnosis.
Our project will use muscle excitability and other neurophysiology techniques to assess patients with hyperthyroidism and muscle weakness prior to and following treatment. With this study, we aim to gain insight into what is occurring at a muscle cell level. This information will result in a greater understanding of hyperthyroid myopathy with the potential to influence future diagnostic testing and treatment.